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Posted by phasmid123 on December 28, 2006, 7:56 pm
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Alun,
Thanks for your insight. For bitlocker's PIN option, you can only use
numbers or you can use characters as well?
JK
Alun Jones [MS-MVP - Windows Security] wrote:
> > Is it true that bitlocker only protects the hard drive when it's
> > OFFLINE? Consider the scenarios:
>
> That is the point of full-drive encryption schemes. When the drive is
> offline, it cannot be brought back online without a key, or set of keys.
> Until it is brought back online with the right keys, the data on the drive
> is essentially random.
>
> > 1) I have a TPM capable laptop running bitlocker. The laptop is NOT
> > joined to a domain and boots automatically to my default account
> > without asking for user logon and password. Let's say this laptop is
> > stolen, the thief can boot it up normally (just like what I do) and
> > transfer the file to another location, correct?
>
> It depends. If you configure the laptop in the default manner - TPM being
> the only protection of the Bitlocker key - then, yes, you are right, the
> thief has everything that he needs to boot your system and copy data out.
>
> > 2) I have a TPM capable laptop running bitlocker. It is not joined to
> > the domain but Windows prompts me to enter a local account name and
> > password before completing the boot process. If I lose this laptop, the
> > thief cannot obtain any data unless the logon and password is known,
> > correct?
>
> Not correct. He does not need your logon and password. He needs to run
> code on your laptop. He can run code either by using your logon and
> password, or by exploiting any flaws that might exist in your operating
> system, attacking it through any of the external ports - network, serial,
> parallel, USB, CD-ROM, Infra-Red, WiFi driver, etc, etc. Are you certain
> that your OS has no such flaws? I'm not, even for Vista.
>
> > What I'm trying to say is, are you only protected by your Windows
> > password with bitlocker? If that your Windows passwd is compromised
> > then the encryption is useless?
>
> You are protected by whatever you use to secure your keys - so set BitLocker
> up to use TPM + PIN or TPM + USB, and don't write the PIN down on a sticky
> note on the laptop case, and don't leave the USB key in the laptop.
>
> You are protected by your Windows password - but since your laptop is
> offline and can't contact the domain controller, the account is not locked,
> and the password can be guessed as many times as the thief cares to try.
>
> You are protected by the security of the code in the Windows Operating
> System - but as soon as a wormable exploit arrives, that protection is void.
>
> You are protected by the strength of the encryption algorithm, and the lack
> of any flaws in it. Mathematics always gets better, though.
>
> By not strongly recommending (and ideally, choosing as default) the options
> in BitLocker that require external keying material (PIN or USB token), I
> think Microsoft have done their users a significant dis-service. By
> insisting that BitLocker + TPM prevents offline attacks, they are
> comfortably ignoring the point that once a machine is stolen, it can be
> brought back online, and the thief can attack the system at his leisure
> through every hole on the outside of your machine (and perhaps a few on the
> inside).
>
> Alun.
> ~~~~
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